The present invention relates to a damping device for telescopic guards.
The invention concerns in particular a damping device for a telescopic guard that consists of a plurality of box-shaped elements connected to each other in pairs and in such a way that they can slide over each other.
Guards of this kind are used typically to protect the guides of automatic machinery, machine tools and robot-controlled equipment to prevent dirt, chippings, and coolant from coming into contact with the guides.
Built into the box-shaped elements there are scrapers, usually made of elastomer or plastic. These scrapers, besides preventing extraneous objects from making their way into the space between two contiguous box-shaped elements, provide a satisfactory seal between the box-shaped elements.
Since the guards concerned are connected to the moving parts of the machines on which they are installed, the box-shaped elements telescopically extend at the same speed as that at which the machine parts move. The speed may therefore be very high and creates a considerable shock between the box-shaped elements when they reach the fully extended position owing to the considerable size and weight of each element. These shocks must obviously be avoided not only to lessen wear on the guards but also to prevent damage to machine parts and to reduce noise.
It is therefore essential to fit damping devices between the box-shaped elements.
An example of a damping device used for this purpose is described in utility patent DE-U-7137781. In this publication, the damping effect is obtained by simply applying a strip of synthetic cellular material to the rear end of each scraper, in the area where it comes into contact with the smaller box-shaped element adjacent to Patent EP-B-290822 discloses another damping device for the box-shaped elements of a telescopic guard. In this case, too, the damping device is made from a strip of synthetic material different from the material which the scraper is made of.
To augment the damping effect of the devices made from strips of synthetic material, the strip of synthetic material may have holes made in it, as described in patent EP-B-502328, in order to make the strip deform more easily.
Despite the use of these damping devices, the guards are still subjected to shocks that are all but negligible on account of the high speeds reached by the moving machine parts, the weight of the box-shaped elements and the limited extent to which the damping devices themselves can be deformed.
Further, when the guards reach the fully extended position, the box-shaped elements come to a complete stop, passing from a very high speed to zero speed in a very small space and in a very short time. They are therefore subjected to a very sudden deceleration which may have damaging effects on the moving machine parts.
Moreover, since the damping devices of the type described above are applied along the entire edge of each box-shaped element, they also have a relatively high cost.
The aim of the present invention is to improve the shock absorbing effect of the elements from which the above mentioned guards are made.
Accordingly, the invention provides a damping device for telescopic guards, said guards comprising a plurality of tubular covering elements that slide inside each other in a defined direction, each tubular element having a front edge and a rear edge, the front edge having a first stop portion which comes into contact with the rear edge of a tubular element when the tubular elements slide out of each other, and the rear edge having a second stop portion which comes into contact with the rear edge of a tubular element when the tubular elements are retracted into each other, the damping device comprising at least one shock absorber located and acting between the rear edge and at least one of the stop portions, said shock absorber comprising a portion for connecting it to the rear edge or to the first stop portion, and at least one flexible arm extending from the connecting portion and comprising at least one damper.